Tried to convince a colleague to give OpenMPT a shot, but they described the UI around the pattern editor (which you can't change the color of, unlike the pattern editor) as a trip to the dentist's office crossed with Microsoft Excel.

Meanwhile, I'm using Windows in dark mode, and... the whole UI is still a glaring white.
Giving the whole tracker a dark mode, and enabling it to be configured separately from the system theme, would go a long way toward improving usability for everyone.